1. Field of the Invention
The invention relates to circuits and methods for linearizing a non-linear signal and producing a predetermined number of corresponding digital outputs each having a predetermined number of bits.
2. Description of the Prior Art
It is well known that many transducers, such as thermocouples, strain gauge bridges, and pressure sensors, and the like are non-linear. Typical control systems frequently include such transducers. Acquisition of data corresponding to the non-linear analog outputs of such transducers is frequently required in the course of operation of the control systems. The data is typically converted from analog form to digital form utilizing an analog-to-digital converter. Use of a high accuracy analog-to-digital converter, such as a 12 bit analog-to-digital converter, results in 2.sup.12 digital output words representing the parameter sensed by the transducer. This is an excessively large number of digital output numbers to store and process. Consequently, in a typical control system it is not practical to "store" each and every data point or to otherwise process each and every data number which can be produced by a high accuracy analog-to-digital converter in response to the non-linear transducer. The process of "linearization" of non-linear data involves selecting a predetermined number of the digital words produced by the analog-to-digital converter and computing or otherwise determining a piece-wise linear approximation of a mathematical curve representing the relationship between the non-linearized data, and the linearized data produced by a "linearizing" system.
Various prior methods of performing such "linearization" have consisted of using non-linear circuit elements or using microprocessors and associated software to perform the linearization function. Non-linear circuits are difficult to design and are generally characterized by low accuracy, instability, and unit-to-unit variation, or are very expensive. Software linearization is more accurate, but usually consumes excessive amounts of time and also requires the expense of incorporating a microprocessor system and developing suitable software therefor. The state of the art in the area of linearization of sensor signals is believed to be indicated by U.S. Pat. Nos. 4,161,880, 3,790,910, 3,662,163, 3,686,665, 3,699,318, 3,939,459, 3,979,745, 4,148,220 and 4,149,120.
Accordingly, it is an object of the invention to provide a low cost digital means of linearizing sensor signals or transducer signals encountered in typical control systems.
Another object of the invention is to provide a digital system and method for linearizing digital signals at sufficiently high speeds that the linearized data can be utilized in conventional successive approximation converter systems.
Still another object of the invention is to provide a linearization system and method which avoids the necessity of utilizing a processor or software in order to accomplish the linearization process.
Yet another object of the invention is to provide a high speed, low cost system and method for linearizing sensor signals with a high degree of accuracy.
A yet further object of the invention is to provide a system and method of linearizing transducer signals without requiring excessive amounts of data storage.